In the manufacture of business forms, it is almost always necessary to seal one part of the form construction with respect to another. This is typically accomplished by utilizing an adhesive which acts between the two portions of the business form to be fixed together. Oftentimes, heat activated adhesives are utilized, but in many circumstances it is desirable to utilize pressure sensitive adhesives.
A sealing system for business forms used with one type of pressure sealing adhesive requires that the adhesive applied to the forms during manufacture be capable of cohesive bonding to a fiber tearing strength when pressure sealed after computer printing by the end user, but must be entirely free of adhesive bonding under all conditions of normal handling during manufacture, storage and imaging. Thus the margins of pressure applied to the paper during normal handling, and the pressure applied to effect fiber tearing bonds are widely separated.
A typical pressure sealing piece of equipment for use with business forms uses a multiple roll sealing system to apply pressure to the entire web (or the entire individual sheets) being processed. Those rolls are capable of exceeding the threshold unit pressure required, which is quite high, typically about 200 lbs. per lineal inch of paper width when using a succession of two or three pressure couples. This requires a very rigid yet accurate mechanical system. While the application of such high forces requires massive and precise construction of the sealer, it is also necessary that the web or sheet manifold be clean--that is that there be no disturbances in the surface configuration. Therefore it is extremely difficult to utilize such equipment with inserts, window patching, folds internal to the form, etc., since such build ups in thickness or non-uniformities in the surface characteristics decrease the unit pressure at the sealing edges and could increase the sealing pressure in the inclusion area so that a jam or physical tearing of the sheet occurs. When inserts are provided, there also is the problem of "tenting" or "pillowing".
In commonly assigned parent application Ser. No. 07/417,775 filed Oct. 6, 1989, expressly incorporated herein by reference, a method and apparatus are provided that overcome certain of the problems associated with full-width pressure sealing systems by making it possible to continuously, and at high speed, act upon business forms including those having inserts, window patching, folds internal to the forms, and other surface non-uniformities. The "pillowing" effects (where the sealed manifold is forced apart), and the "tenting" effects (where various plies of the assembly shift relative to each other and thereby prevent formation of a completely flat form) are substantially avoided.
The general manner in which these results are accomplished according to the above identified application is by effecting sealing along only the pressure sensitive adhesive strips of the business forms--rather than along the entire surface of the forms. This allows the coupling force between each sealing roll pair to be reduced from about 1,000 lbs. in the prior art, to about 100-200 lbs., dependent on the ratio of total form width to sealing bond width. This also allows production of a system that is much less massive than conventional, and one that is reliable and simple and easy to utilize.
There may be disadvantages in the above described system, however. For example, in order to apply pressure to adhesive strips extending transverse to the longitudinal edges of the form, the latter is turned ninety degrees and fed sideways through a second sealer. In other words, longitudinal edge sealing is achieved with the forms passing between a roll pair in the grain direction, while a second roll pair acts on the form in a direction 90.degree. from the grain direction. While the concept of narrow pairs of rollers under high pressure effect the seal of the perimeter of forms with inserts quite satisfactorily in the grain direction, some wrinkling can occur in the direction perpendicular to the grain direction.
The objective of the invention is to expand the concept of perimeter sealing as disclosed in the above identified co-pending application by applying sealing pressure to both the longitudinal and transverse adhesive strips while the forms are traveling in a single orientation and in a single direction, i.e., the grain direction of the paper.
It will be appreciated, however, that the transversely extending sealing strips, which will usually be of greater length than the transverse sectional length of the longitudinally extending margin strips, will require greater force between the cooperating rotary couples (or roll pairs) to effect the same unit pressure. For example, an 11" wide document, with a 101/2" transverse sealing length, and with two marginal strips each 1/2" wide (for a total of 1") will require 10.5/1 or 10.5 times the force to effect the same sealing pressure on the transverse strip as on the longitudinal margin strips. This can be accomplished if separate longitudinal sealing wheels and transverse sealing segments are used, by simply so selecting the spring force necessary to impact the desired sealing pressure of about 150 pounds per lineal inch.
In the case of a combined longitudinal/transverse sealing wheel, this same result could be accomplished by providing a slightly reduced diameter on the longitudinal sealing portion of the sealing wheel to thereby reduce the effective unit pressure on the longitudinally extending strips to more nearly approximate or equal the unit pressure on the transverse sealing strips.
Thus, in accordance with one exemplary embodiment, perimeter sealing of the form is achieved by two sets of spring-loaded roll pairs, the upper roller of each set having enlarged circumferential sealing surfaces at opposite ends thereof for sealing the longitudinal marginal edge portions of the form, and a transverse sealing bar extending between the longitudinal sealing surfaces for sealing the transverse marginal edge portions of the form.
In this arrangement, the form is fed toward the roll pairs until the forward edge of the form engages a stop gate which serves to establish proper timing and registration for the form relative to the transverse sealing bar of the first roll pair. Upon retraction of the gate, the form will be fed between the rollers of the first roll pair to thereby activate the pressure sensitive adhesive along the forward transverse marginal edge and the longitudinal edges of the form. After the form has passed completely through the first roll pair, it engages a second stop gate where timing and registration is again established to insure engagement of the second transverse sealing bar with the second or rearward transverse marginal edge of the form. Upon retraction of the second gate, the form passes between the rollers of the second roll pair to activate the pressure sensitive adhesive along the rearward transverse marginal edge, while at the same time, the longitudinal marginal edge portions of the form are again pressed in a redundant or back-up sealing action.
It will be appreciated that the spacing between the two roll pairs in the direction of travel of the forms may be adjusted as required. At the same time, sequencing and control of the gate stops and the drive means of the two roll pairs may be accomplished electronically or mechanically in accordance with conventional control technology. As a result, the rotational velocity of the rollers and the rate of feed of the forms may be coordinated so as to permit the two roll pairs as described above to longitudinally and transversely seal business forms of virtually any length, but with a fixed width.
In a second exemplary embodiment, the longitudinal edge sealing and transverse edge sealing of each successive form is carried out separately, i.e., with two roll pairs effecting transverse edge sealing, substantially as described above, and two pair of laterally aligned rollers upstream or downstream of the two transverse edge sealing roll pairs for effecting longitudinal edge sealing. These longitudinal edge sealing rollers are of the type described, for example, in the pending parent application. In this second embodiment, the transverse edge sealing rollers have lengths greater than the widths of the forms so that the enlarged circumferential edges of the upper rollers directly engage surfaces of associated lower rollers, and so that the forms pass between but out of contact with these enlarged edge surfaces. Thus, the enlarged edge surfaces have a bearing function only, without any pressure sealing function.
Here again, this arrangement may be adapted to handle any length form. In addition, since the transverse edge sealing rollers have lengths greater than the width of the forms, the apparatus as described in this second embodiment can accommodate forms of different widths when combined with laterally adjustable longitudinal edge sealing rollers.
In a third exemplary embodiment of the invention, a single roll pair may be employed to seal both the longitudinal and transverse edges of each form. In this embodiment, the upper roller of the roll pair has raised circumferential edge surfaces for sealing the longitudinal edges of the forms, and a single raised transverse edge sealing bar. Stated otherwise, the upper roller is relieved in those areas corresponding to the center area of the form, within the transverse and longitudinal marginal edges thereof. This embodiment is intended for dedicated applications, i.e., where single length and single width forms are to be processed. Thus, the transverse sealing bar and the form feed will be adjusted so that the transverse sealing bar pressure activates the forward transverse seal and, upon rotation through 360.degree., the same bar will pressure activate the rearward transverse seal. At the same time, the longitudinal edge seals are pressure activated by the raised circumferential surfaces at either end of the upper roller.
It will be appreciated from the above that the circumference of the pressure roller will be substantially identical to the form length.
In a fourth exemplary embodiment, two sets of length-adjustable roll pairs are provided in spaced relationship, in the direction of movement of the forms, each set having a longitudinal edge and transverse edge sealing function. This embodiment permits perimeter sealing of forms having different lengths and different widths.
To this end, the rollers of each roll pair are of a telescoped construction so that the length thereof may be adjusted to accommodate forms of different widths.
In each of the above described embodiments where longitudinal and transverse sealing surfaces are provided on a single roller, the longitudinal edge sealing surfaces may have slightly reduced diameters (or radii) as compared to the intermediate roll diameter (or radius, as determined by the distance from the roll center axis to the transverse sealing surface) in order to more nearly equalize the longitudinal and transverse sealing pressures.
Thus, in its broader aspects, the present invention relates to a method of handling business forms, each having at least two strips of pressure sensitive adhesive of a predetermined width for fixing one part of the business form to another part, and wherein one of the strips of pressure sensitive adhesive extends substantially perpendicularly to the other, comprising the step of (a) automatically, in a continuous, sequential manner, acting on successive business forms aligned in a predetermined orientation and fed in one direction of movement to apply a force thereto sufficient to activate the pressure sensitive adhesive to fix one part of the form to another, the force being applied only to the approximate area of the predetermined widths of the two strips of pressure sensitive adhesive, without having to alter the predetermined orientation or one direction of movement.
From an apparatus standpoint, the invention relates broadly to a system for pressure activation of a plurality of pressure sensitive adhesive strips located in marginal edge portions of a business form, wherein at least two of the plurality strips are arranged perpendicular to each other, the apparatus comprising: a first roll set for activating one of the two pressure sensitive adhesive strips; a second roll set for activating the other of the two pressure sensitive adhesive strips, wherein the first and second roll sets rotate about parallel axes.
In a related aspect, the invention relates to apparatus for pressure activation of first and second longitudinally extending pressure sensitive adhesive strips located in longitudinal marginal edge portions of a business form, and third and fourth transversely extending pressure sensitive adhesive strips located in transverse marginal edge portions of the business form, the apparatus comprising: a first roll pair including upper and lower rollers, one of the upper and lower rollers formed with enlarged end portions and a first transverse sealing surface extending between the enlarged end portions for activating one of the third and fourth transversely extending pressure sensitive adhesive strips; a second roll pair including upper and lower rollers, one of the upper and lower rollers being formed with enlarged end portions and a second transverse sealing surface extending between the enlarged end portions for activating the other of the third and fourth transversely extending pressure sensitive adhesive strips.
Other objects and advantages of the invention will become apparent from the detailed description which follows.